The increasing reliance on communication networks to transmit more complex data, such as voice and video traffic, is causing a very high demand for bandwidth. To resolve this demand for bandwidth, communication networks are relying more upon optical fibers to transmit this complex data. Conventional communication architectures that employ coaxial cables are slowly being replaced with communication networks that comprise only fiber optic cables. One advantage that optical fibers have over coaxial cables is that a much greater amount of information can be carried on an optical fiber.
The Fiber-to-the-home (FTTH) optical network architecture has been a dream of many data service providers because of the aforementioned capacity of optical fibers that enable the delivery of any mix of high-speed services to businesses and consumers over highly reliable networks. Related to FTTH is fiber to the business (FTTB). FTTH and FTTB architectures are desirable because of improved signal quality, lower maintenance, and longer life of the hardware involved with such systems. However, in the past, the cost of FTTH and FTTB architectures have been considered prohibitive. But now, because of the high demand for bandwidth and the current research and development of improved optical networks, FTTH and FTTB have become a reality.
A conventional hybrid fiber-to-the-home (FTTH)/hybrid fiber-coax (HFC) architecture has been proposed by the industry. HFC is currently the architecture of choice for many cable television systems. In this FTTH/HFC architecture, an active signal source is placed between the data service hub and the subscriber. Typically, in this architecture, the active source comprises a router. This conventional router typically has multiple data ports that are designed to support individual subscribers. More specifically, the conventional router uses a single port for each respective subscriber. Connected to each data port of the router is an optical fiber which, in turn, is connected to the subscriber. The connectivity between data ports and optical fibers with this conventional FTTH/HFC architecture yield a very fiber intensive last mile. It noted that the terms, “last mile” and “first mile”, are both generic terms used to describe the last portion of an optical network that connects to subscribers.
In addition to a high number of optical cables originating from the router, the FTTH/HFC architecture requires radio frequency signals to be propagated along traditional coaxial cables. Because of the use of coaxial cables, numerous radio frequency (RF) amplifiers are needed between the subscriber and the data service help. For example, RF amplifiers are typically needed every one to three kilometers in a coaxial type system.
The use of coaxial cables and the FTTH/HFC architecture adds to the overall cost of the system because two separate and distinct networks are present in such an architecture. In other words, the FTTH/HFC architecture has high maintenance cost because of the completely different wave guides (coaxial cable in combination with optical fiber) in addition to the electrical and optical equipment needed to support such two distinct systems. More simply, the FTTH/HFC architecture merely combines an optical network with an electrical network with both networks running independently of one another.
One problem with the electrical network in the FTTH/HFC architecture involves cable modem technology which supports the data communications between the data service provider and the subscriber. The data service subscriber typically employs a cable modem termination system (CMTS) to originate downstream data communications that are destined to the subscriber. To receive these downstream data communications, the subscriber will typically use a cable modem that operates according to a particular protocol known in the industry as Data-Over-Cable-Service-Interface-Specification (DOCSIS). The DOCSIS protocol defines service flows, which are identifications assigned to groups of packets by the CMTS for the downstream flows based on an inspection of a number of parameters in a packet.
More specifically, a service flow is a media access control (MAC)-layer transport service that provides unique directional transport of packets either to upstream packets transmitted by the cable modem or to downstream packets transmitted by the CMTS. The identifications assigned to groups of packets in the DOCSIS protocol can include parameters such as TCP, UTP, IP, LLC, and 802.1 P/Q identifiers contained in an incoming packet.
Based on these identifications, the CMTS assigns a service flow ID (SFID) to a particular datastream. A service flow typically exists when the CMTS assigns this SFID to a datastream. The SFID serves as the principle identifier in the CMTS for the service flow. A service flow is characterized by at least an SFID and an associated direction. One of the main drawbacks of the DOCSIS protocol for downstream data communications is that this protocol does not offer any guaranteed bandwidth. In other words, every cable modem in a particular subscriber group competes for bandwidth in both the upstream and downstream directions when a particular modem needs it. This competition between modems for bandwidths can significantly affect the quality of service of data communications for each individual cable modem receiving downstream data communications.
For example, subscribers that desire to use their cable modem for T1 communications require a constant bit rate and consistent arrival time of packets in order to reduce any jitter in the communications. T1 communications can include telephone calls, video conferencing, and other similar traffic. Because each cable modem according to the DOCSIS protocol competes for bandwidth, it is possible that some cable modems will not be provided with a constant bit rate for their T1 communications. In such a scenario, the quality of T1 communications can suffer. That is, during a telephone call or a video conference the subscriber may notice either delays in communications or truncation in conversations with the other party to the telephone call or video conference.
DOCSIS is designed to operate over an RF modulated network, which imposes certain restrictions on the protocol. Return bandwidth is low relative to downstream bandwidth, as a result of the way spectrum is apportioned in the two directions. This causes problems with certain applications requiring more symmetrical bandwidth. These applications include peer-to-peer file transfer, video conferencing and communications from web servers.
Accordingly, there is a need in the art for a system and method for communicating optical signals between a data service provider and a subscriber that eliminates the use of coaxial cables and related hardware and software necessary to support the data signals propagating along the coaxial cables. There is also a need in the art for a system and method for communicating optical signals between a data service provider and a subscriber that can service a large number of subscribers while reducing the number of connections at the data service hub.
There is also a need in the art for a method and system for handling downstream optical communications that can police or monitor downstream bandwidths for quality of service at exit portions of the optical network. There is a further need in the art for a system and method that can allocate additional or reduce downstream bandwidths based upon one of demand or the type of service selected by one or more subscribers of an optical network. There is also a need in the art for a method and system for controlling the volume or content (or both) of downstream optical communications that are received by subscribers of an entirely optical network.